This invention relates to photodetectors which will respond to light of wavelengths extending beyond the red end of the visible spectrum into the near infrared, and more particularly to application of internal photoemission from quantum-well structures to such infrared detectors.
The advent of molecular beam epitaxy makes possible the growth of ultrathin crystal layers of high quality, and therefore the fabrication of devices with complicated band structures and a high degree of control over important parameters such as doping profiles, band discontinuities, and layer thicknesses. High quality large-area wafers may be grown with layer thickness control of a few angstroms. An object of this invention is to provide a new type of infrared photodetector which allows this high degree of control to enable the tailoring of such characteristics as its cutoff wavelength and the tradeoff between its photoconductive gain and response time.